Why are timber buildings suddenly becoming more popular?

No longer relegated to ‘structures of a certain size’, timber buildings are making a comeback – and moving up in the world.

The first and strongest reaction anybody has when they see an artist’s impression of the 300 m tall Oakwood Tower, looming above London with its 80 floors of wooden glory, is relaxation, says Kevin Flanagan, Partner at PLP Architecture and one of the head designers on the timber tower. They don’t become worried about fires or begin asking questions about what kind of havoc termites could wreak in timber buildings like this one.

Instead they simply relax, then they ask the designers how soon it’s going to be built because they are engaged and want to buy in.

“Wood is good,” Flanagan said.

“People respond positively to wood as if they are living in or viewing nature. In California about 85 per cent of new children’s schools are built from wood. No doubt due to savings in time and cost thanks to the ability to prefabricate building parts, but also studies of how timber in classrooms benefit children’s learning. Even those with learning disabilities concentrate better in this more natural setting.

“Wood is calming, it seems, for children and they are therefore more sociable and have lower heart rates due to lowered environmental stress. Likewise, people in cities have an equally positive reaction to timber. For this high-rise concept we imagine that in an ever-denser urban environment our quality of life could be greatly improved.”

Designed to look like giant mushrooms, the Metropol Parasol towers over a market square in Seville, Spain.

Anybody who has been to Europe has witnessed the grand, strong and timeless nature of timber buildings. Cathedrals, railway stations and apartment complexes regularly contain timber as at least a part of their major structural elements. But still wood has traditionally been perceived as a building material reserved for low-rise applications.

The Oakwood Tower team begs to differ. The gorgeously designed and multiple award-winning architectural marvel – originally inspired by a research project being managed by Dr Michael Ramage, director of the Centre for Natural Material Innovation at Cambridge University, with Simon Smith of SaW Engineers – made the world sit up and realise that timber is not just for houses. But could the Oakwood Tower be built today?

“The team at Cambridge is currently challenging manufacturers to see if they can build the columns, or piers, at the base of the building – they are about 2.5 m by 2.5 m – from a laminate or cross laminate engineered timber,” Flanagan said.

“They’re testing the column manufacturing processes that would allow them to proceed with that type of scale. They are pushing the industry in the direction of high-rise design as a test case.”

Timber buildings in Australia

When CEO of the Timber Development Association, Andrew Dunn, took a group of politicians into Melbourne’s 10-storey Forte (which markets itself as the world’s tallest timber apartment building) it was a hot summer day. But once inside, the visitors asked if somebody had left the air conditioning on.

“The difference was that it was a humid heat outside but a dry heat inside, so it automatically felt cooler,” Dunn said.

“Wood is hygroscopic, meaning that on high heat days it takes in moisture, so it dries the air. It works in reverse as well. When it’s uncomfortably dry inside, the wood will release moisture.”

It is Dunn’s job to convince various parts of the engineering, architecture and building industries of the value of timber as a building product. He is under no illusion that it will ever completely replace concrete and steel, but sees value in timber being utilised more heavily thanks to its many benefits.

“It’s no longer a two-horse race in the selection of building materials,” Dunn says.

“Engineers should now consider timber on equal terms with concrete and steel.”

Forte in Melbourne’s Docklands is one of the world’s tallest timber apartment buildings.

Timber allows for a faster build, for instance, meaning the build should theoretically cost less and people in neighbouring buildings will suffer fewer construction disturbances. It is also much lighter than other structural materials, and can therefore be used to add floors to old buildings without significantly taxing the existing structure, can be designed to provide excellent seismic resistance and can reduce costs on poor foundation building sites.

“There are enormous benefits, but not every building can be a timber building,” Dunn said.

“Timber has certain constraints, just like other materials. There are different reasons a steel building works, or reinforced concrete works. I don’t see the end of concrete or steel. There always will be a need for those materials.

“But there is plenty of wood around in forests being grown to feed such industries as paper. I don’t see any shortage of wood. What we need to do right now is to work on our supply chain.”

There’s a growing demand for timber products and the timber industry now has to work to meet demand, Dunn explained.

“We look at Europe, where these products have been well and truly utilised for a long time,” he said.

“Anything in Central Europe up to five or six storeys is built from wood, including exhibition halls, petrol stations, supermarkets etc. They’re 20 or 30 years ahead of us and they have a supply chain that is very competitive. We are in the process of developing that supply chain in Australia.”

Light, strong and safe

During his final year of an undergraduate degree in structural engineering Dr James O’Neill, now a fire engineer with Holmes Fire LP in Sydney, took a course on timber design. The degree had largely concentrated on concrete and steel, but it was his late introduction to timber that truly captured O’Neill’s interest.

“We had a foreign lecturer come in. He said in Europe they worked a lot with timber buildings, that it’s quite a big thing over there. I was hearing amazing things about how they have old masonry buildings in Germany that are five storeys high and they put another four stories on top of them in timber. Because the timber structure is so light, the existing building structure can support it. If you wanted to do this in concrete you’d be looking at just one storey, so it wouldn’t be feasible,” O’Neill said.

“It made me realise the potential of timber for larger applications. Obviously there are the added benefits in terms of sustainability, which is always a big marketing bonus for timber, but it’s more than that. In Europe and particularly in countries like Switzerland and Sweden they’re making fantastic use of timber.”

Glulam, short for glued laminated timber, is produced by gluing together separate laminates. It’s regularly used for trusses, rafters, columns, beams and more.

Engineered timbers such as glulam and laminated veneer lumber (LVL) have made timber stronger, more versatile and more dimensionally stable than traditional sawn timber, O’Neill said. These timber products can be comparable in strength to concrete and steel. From an engineering perspective, there is no longer any argument to stop engineers from building tall buildings using timber.

From a public perception angle, however, it may be a different story. The biggest concern in people’s minds is fire, O’Neill said.

“The thing is, we’re not talking about small sticks of wood that burn easily,” he said.

“We’re talking about massive sections containing fire-resistant adhesives, sections that could be half a metre wide and 20 m tall.

“We’re talking about massive pieces of wood that take a very long time to burn in a fire. As the timber section burns, it develops an insulating char layer on the outside that protects the remaining timber inside from heat. In this way, the timber member will continue to carry building loads in a fire when other materials might have already failed.

“A building made from timber requires the same fire safety measures, including sprinklers, as any other building. The higher the building, the greater the degree of fire protection, no matter what the building is made from, as it is primarily based on risk. But, most importantly, any risks relating to the combustibility of timber can be easily mitigated with good fire engineering practices.”

Why timber now?

Why the seemingly sudden interest in timber as a building product for tall buildings? It has a lot

to do with the advent and continual development of the computer numeric control (CNC) machine.

“Instead of it being a very labour intensive process to produce a beam that is cut to the absolutely perfect dimensions, it is now put on the machine and accurately shaped,” Dunn said.

The machinery has allowed for the engineering of wood. Rather than simply sawing a log from the hardest part of the tree, pieces are now accurately shaved from the log then put back together with glue or nails in order to create something far stronger, larger and longer lasting than the sum of its parts.

And so we are seeing sculptural bridges, stunning buildings and more being created from once humble timber, but really it’s nothing new.

“China’s Pagoda of Fogong Temple was built in 1056, is 67 m tall and, apart from a stone base, is fully wooden,” O’Neill said.

“Evidence of the strength, beauty and endurance of timber buildings is all around us.”

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